Several types of current sensors can be utilised in an electricity counter and are described in FR 2 800 167.
In particular, sensors with Hall effect are known, in which a Hall element is subjected to a magnetic field generated by a current in a primary winding. The Hall tension measured at the terminals of the Hall element is proportional to the current crossing this primary winding.
Another type of known sensor makes use of a transformer with mutual inductance. This type of sensor comprises for example a primary conductor having a the general form of an open U-shaped loop and a secondary winding sensitive to a magnetic field and wound on a winding placed inside the primary conductor. The secondary winding is subjected to a magnetic field generated by a current passing through the primary conductor, and the signal available at the terminals of the secondary conductor of the transformer is the image of the derivative as a function of the signal time applied to the primary. The primary conductor is a solid cylindrical conductor cable traversed by the current to be measured and whereof the ends are fixed in contact terminals situated on the counter.
The latter solution poses certain difficulties, however.
Therefore, in the case of an increased measuring current, the diameter of the primary cable must be relatively significant to cause an increase in the section of the cable. This raised section causes augmentation in size, especially in width, and overall cost of the current sensor.
In addition, because the electricity counters are becoming smaller and smaller, it is likewise necessary to make the current sensors as compact as possible.
In addition, there are different types of contact terminals allowing the counter to be connected to the ends of the primary conductor. The different forms of these terminals necessitate modifying the structure of the primary cable, which is fairly difficult to handle due to its solid cylindrical form.